Washington Redskins defensive end Jarvis Jenkins has been suspended the first four games of the season for violating the league’s policy on performance enhancing drugs.

The news apparently came as a surprise to Jenkins, who said he isn’t sure how the “obscure substance” got into his body. He added that he was taking a supplement that was not banned.

The suspension puts the Redskins in a tough spot. Jenkins’ backup, Adam Carriker, is out for at least four months with a quadriceps injury.

Jenkins is suspended without pay, but can participate in training camp and preseason games. He is eligible to return to action September 30.

"When I learned that I tested positive for a substance that is banned under the NFL policy, I was shocked and confused," he said in a statement Friday. "It's an obscure substance that I've never even heard of, and I still don't know how it got into my body. My only guess is that it came from one of the supplements I was taking around the time of the test, even though none of them listed anything banned."

The Redskins have experienced a spate of drug-related suspensions lately. In addition to Jenkins, reserve linebacker Rob Jackson is also suspended for the same reason.

According to the Washington Post, at least eight players have been suspended over the past three seasons for violations of the league's two drug-related policies—substance abuse and performance enhancing drugs.

Last year alone was a bad one in this area. Cornerback Cedric Griffin was banned from the final four games of last season. Tackle Jordan Black, who has been released from the team, was suspended on Dec. 17 and after sitting out three games, still owes the NFL another game before he can return. He is eligible to participate in offseason workouts, when and if another team signs him. Safety Tanard Jackson was suspended the entire season for violating the substance abuse policy. He will be eligible for reinstatement in late August. The Redskins will get a roster exemption and have time to decide whether to bring Jackson back.

As for Jenkins, he had high hopes for the year. Jenkins tore his ACL as a rookie in 2011 and bounced back last year with a solid season that included 25 tackles. He was fully expected to build on that.

"I will be very, very ready to contribute as soon as I get back for Game 5," he said.

He’s the second player in a week to be suspended for a violation of the league’s drug policy. Broncos linebacker Von Miller is appealing a four-game suspension. The NFL Players Association confirmed to USA Today that it is helping Miller with his appeal.

“I know I did nothing wrong,” Miller wrote on his Twitter page. “I’m sure this will be resolved fairly.”